Outline2 - Outline 2 Introduction to the Nervous System I...

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1 Outline 2 Introduction to the Nervous System I. Major Players: Neurons & Glia A. 1. Neurons ("nerve cells") - cells that receive information and transmit it to other cells by conducting electrochemical impulses -Approximately 100 billion neurons in the adult human brain -Each neuron forms 10's to millions of connections with other neurons -The sites of these connections are synapses (aka synaptic connections ) 2. Glia (aka "neuroglia" for nerve glue, aka glial cells ) about 10X's as many glial cells as neurons in brain and they occupy approximately the same amount of space as neurons a. Macroglia 1. astrocytes 2. oligodendrocytes (CNS) 3. Schwann cells (PNS) b. Microglia - brain macrophages- immune function B. Very Basics of Neurons
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2 (1) Basic structure of the neuron dendrites dendritic spines (some neurons) cell body (aka soma, sing., somata, plura) axon initial segment of axon (aka, axon hillock) axonal arbors (aka axonal ramifications, axonal branches) nodes of Ranvier-- found in myelinated axons axonal boutons, varicosities and "terminals" "en passant" terminals myelin sheath (some neurons) (2) Major microstructure nucleus -contains chromatin (chromosomes-long strands of DNA)--transcription (RNA/ "gene expression") (translation -> new proteins) mitochondria -energy producers (oxidative metabolism) cytoplasm -"gel" containing a matrix of filaments making up the cytoskeleton: microtubules -largest filaments--participate in trasport of substances within the cells
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3 neurofilaments - found in axons but not dendrites microfilaments -finest filaments polyribosomes -packets of ribosomes (RNA and proteins) that synthesize proteins. Polyribosomes are found either free in the cytoplasm, in aggregates ("polyribosomal aggregates") or studding endoplasmic reticulum Golgi bodies - packaging of substances into vesicles (3) Membranes Lipid bilayer studded with proteins -these proteins form channels and receptors II. Directions: dorsal-ventral rostral-caudal (anterior-posterior) medial-lateral Planes: sagittal/coronal/horizontal
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4 III. Major Parts of the Nervous System A. Divisions of the Nervous System 1. Central Nervous System (CNS) a. Brain b. Spinal Cord- communicates with sense organs and muscles below the head -segmented structure. -each segment has a sensory nerve (input) and a motor nerve (output) on both the left and right side. - the central canal lies at midline and is filled with cerebral spinal fluid The brain and spinal cord are made up of both white matter -mainly axons traveling too and from places, and gray matter which includes neurons and their connections
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5 2. Peripheral Nervous System (PNS) Cranial Nerves (head and upper body) and Spinal Nerves -connect the CNS with the muscle and organs of the rest of the body a. Somatic Nervous System--
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